1. Field of the Invention
Embodiments herein present a method, computer program product, etc. for masking data failures.
2. Description of the Related Art
Today, data management systems pass on failure events during data accesses or updates to application programs. For read-only queries, there is prior work. on making failures by providing partial results to the application programs. But masking failures for applications that do updates is much harder because there is no notion of a partial update. Today, because there is no failure masking, the application programmer has to program for the error condition. For example, an application that is inserting records into a database needs to buffer its updates, periodically poll the data source to see if it has come back up, and then apply its updates once the sources are available. Even this solution is incomplete because subsequent reads from the same application will not see these updates unless the programmer adds special logic.
In file systems, there has been work on disconnected operation, where application programs perform updates against local copies of files. Files are treated as atomic objects and it is assumed that a local copy of the entire file is available. When an application gets disconnected from a master copy, the local copy is a single atomic object that the application updates. The problem listed above—that the application should see both its updates and the existing data while the source is down—is trivial for files because by definition disconnected operation is possible only if there is a local copy, and all the updates and reads are performed on this local copy.
An alternative way of handling failures is through a high-availability cluster HACMP. This ensures that there is always an alternate server that can provide the data if the original server fails. The disadvantage is that it is not transparent to the application. The application must be redirected against the alternative. A very different style of solution to this problem is to assume a peer-to-peer replication environment where there are multiple master copies of the data. In view of the foregoing, it is readily apparent that there is a need for a method, computer program product, etc. for effectively masking data failures.